1. Field of the Invention
The present invention relates to a projector device, and more particularly to a projector device for projecting images on a screen by using a digital micromirror device (DMD).
2. Description of the Related Art
A DMD comprises a large number of micromirrors arranged in a matrix, in which each micromirror constitutes one pixel of a displayed image. Each micromirror can take one of two inclined states, an ON state and an OFF state. In the ON state, illuminating light is reflected into a projecting optical system, while in the OFF state it is projected away from the projecting optical system. Therefore, in a projector device using a DMD, the projecting optical system projects only the light reflected by micromirrors in the ON state, resulting in the formation of a displayed image composed of a pattern of different levels of brightness on the screen.
Known projector devices using such a DMD include ones disclosed in Japanese Patent Application Publication Nos. 9-98442 and 12-206452.
FIG. 7 shows a plan of a micromirror drive structure in a DMD, and FIG. 8 shows the 8xe2x80x948 section in FIG. 7. The drawings show expanded views of one extracted out of many micromirrors constituting the DMD, which actually is configured of a large number of micromirrors arranged in a matrix.
As illustrated in FIG. 7 and FIG. 8, a micromirror 2 of a DMD 1 can take either an ON state inclined by +10xc2x0 or an OFF state inclined by xe2x88x9210xc2x0 to the DMD surface by turning around a rotation axis ab. This rotation axis ab of the micromirror 2 is set in a direction inclined by 45xc2x0 to the long or short side of the DMD 1, and illuminating light Lo irradiates the surface of the DMD 1 at an incidence angle of 20xc2x0 in a direction orthogonal to this rotation axis ab.
The illuminating light Lo irradiating the DMD, if reflected by the micromirror 2 in the ON state, turns into a projecting light L1 whose angle of reflection by the surface of the DMD 1 is 0xc2x0 or, if reflected by the micromirror 2 in the OFF state, turns into projecting light L2 whose angle of reflection by the surface of the DMD 1 is xe2x88x9240xc2x0. Only the projecting light L1, which is a luminous flux reflected by the micromirror 2 in the ON state at 0xc2x0 in the angle of reflection, comes incident on the projecting optical system, and a displayed image composed of a pattern of different levels of brightness is formed on the screen.
Incidentally, for a projector device using a DMD as stated above, on account of the above-described structure of the DMD 1, the illuminating optical system has to be configured to meet two constraints that the illuminating light Lo should be brought to incidence in a direction orthogonal to the rotation axis of the micromirror 2 (a direction inclined by 45xc2x0 to the long or short side of the DMD) and the illuminating light Lo should further be brought to incidence at an angle of 20xc2x0 to the surface of the DMD 1.
In a projector device according to the prior art, as shown in FIG. 9 and FIG. 10, a total internal reflection prism (TIR prism) is used to irradiate the DMD with illuminating light from a light source. Thus, light emitted from a light source 3 is condensed into a rod integrator 4, guided by a first mirror 5 and a second mirror 6 to a TIR prism 7 and totally reflected by that TIR prism 7 thereby to irradiate the DMD 1 in a required direction (a direction inclined by 45xc2x0 to the long or short side of the DMD 1) and at a predetermined incidence angle (20xc2x0). By causing the illuminating light irradiating the DMD 1 in this way to be reflected by the DMD 1, optical modulation is performed, and the light transmitted by the TIR prism 7 after that optical modulation is projected by a projecting optical system 8 onto a screen.
However, this projector device according to the prior art, since the illuminating light should be brought to incidence on the DMD 1 in an oblique direction as shown in FIG. 10 to meet the two constraints stated above and fixed in that state, involves the disadvantage of permitting no reduction in its overall thickness.
An object of the present invention, attempted in view of this circumstance, is to provide a projector device that permits a reduction in thickness.
In order to achieve the object stated above, the present invention is directed to a projector device in which illuminating light from a light source is guided by an illuminating optical system to a digital micromirror device and irradiates the digital micromirror device at a predetermined incidence angle and in a predetermined direction, and light modulated by the digital micromirror device is projected by a projecting optical system on a screen, wherein: the direction of irradiation of the digital micromirror device with the illuminating light by the illuminating optical system is made variable depending on whether the projector device is used or unused.
According to the invention, the irradiating direction of the DMD with the illuminating light by the illuminating optical system can be varied depending on whether the device is used or not used. Therefore, by irradiating the DMD with the illuminating light in the predetermined direction only when the projector device is used, the overall thickness of the device can be reduced when it is not used.
The present invention is also directed to a projector device in which illuminating light from a light source is guided by an illuminating optical system to a digital micromirror device and irradiates the digital micromirror device at a predetermined incidence angle and in a predetermined direction, and light modulated by the digital micromirror device is projected by a projecting optical system on a screen, wherein: the digital micromirror device is provided rotatably around a rotation axis vertical to the digital micromirror device, at least part of the illuminating optical system is provided rotatably around the rotation axis so as not to let the direction of irradiation of the digital micromirror device from the illuminating optical system vary, and when the projector device is in use the inclination of the image projected on the screen is corrected by rotating at least part of the illuminating optical system and the digital micromirror device around the rotation axis.
According to the invention, the DMD is provided rotatably around a rotation axis vertical to the DMD and at least part of the illuminating optical system is provided rotatably around the rotation axis so as not to let the direction of irradiation of the DMD from the illuminating optical system vary. When the device is in use, the inclination of the image projected on the screen is corrected by rotating at least part of the illuminating optical system and the DMD around the rotation axis. This makes it possible to configure a projector device reduced in thickness when it is not in use.